Laminated unit

ABSTRACT

A laminated panel unit ( 1 ) comprising at least one image layer ( 3 ) between at least two panels ( 2 ), wherein for an area-contact gluing of the image layer ( 3 ) with neighboring panels ( 2 ), one intermediate adhesive layer ( 4, 4 ′) is provided on each side thereof, wherein the two intermediate adhesive layers and/or panels following each image layer ( 3 ) have a different thermal expansion behavior so that the image layer ( 3 ), due to the inhomogeneous laminate, is tensioned in case of temperature changes; as well as a method for producing a laminated panel unit ( 1 ), wherein the image layer ( 3 ) is connected with area contact on either side thereof with the panels ( 2 ) by using intermediate adhesive layers ( 4, 4 ′), the intermediate adhesive layers ( 4, 4 ′) and/or the panels ( 2 ) having a different thermal expansion behavior.

[0001] The invention relates to a laminated panel unit comprising atleast one image layer between at least two panels, wherein for anarea-contact gluing of the image layer with neighboring panels, oneintermediate adhesive layer is provided on each side thereof, as well asto a method for producing the laminated panel unit according to theinvention. The image layer may have any optic image desired, includingparticularly also writings.

[0002] From U.S. Pat. No. 5,595,794 A, a laminated glass unit is knownin which, for keeping archives of photograph material, the photograph isglued between two glass panes by means of two adhesive polyurethanelayers, whereby a five-layer laminate is formed. However, such alaminated glass unit is only suitable for interior archiving, and eventhis to a limited extent only, since already with relatively slighttemperature fluctuations the adhesive polyurethane layers of thelaminated glass unit will expand upon heating, whereby the photographenclosed between the two glass panes will become wavy, resulting in anoptically negative, unacceptable change of the photograph materialenclosed in the laminated glass unit.

[0003] A somewhat different laminated panel unit which comprises avisible (motif) pattern is described in WO 95/00329 A1. A visiblepattern is applied to a plastics sheet, e.g. a polyvinyl butyral sheet,by means of an epoxy-resin-based printing ink and is dried on thepolyvinyl butyral sheet before the laminated unit is assembled. Moreprecisely, an ink layer is used by silk-screening to produce a pattern,and only one single plastics sheet, i.e. polyvinyl butyral sheet, isused to interconnect two glass panes or plastics panels.

[0004] JP 56-45852 A shows a method of producing stained glass, whereindepressions are technically produced in a resin layer in which finallythe desired dyes are injected.

[0005] It is now an object of the present invention to provide alaminated panel unit of the initially defined kind, which ensures anoptically perfect rendering of the image layer enclosed between thepanels even in case of temperature fluctuations. Therewith, inparticular, also a laminated panel unit is to be created which can beused externally, e.g. as facade glass-work, windows and the like, andwhich will withstand also the substantial temperature fluctuationsoccurring outside. Furthermore, it is an object of the invention toprovide a method for producing the inventive laminated panel unit.

[0006] The inventive laminated panel unit of the initially defined typeis characterized in that the two adhesive intermediate layers and/orpanels following each image layer have a different thermal expansionbehavior so that the image layer, due to the inhomogeneous laminate, istensioned in case of temperature changes. With the help of the twolayers neighboring the image layer (intermediate adhesive layer, panel),whose thermal expansion behavior differs, the image layer is heldtensioned between the two panels even if the laminated panel unit isheated. Thus, the image layer enclosed between the two panels can beprevented from becoming wavy, and also the formation of blisters can beavoided, since the different thermal expansions on the two sides of theimage layer will result in an inhomogeneous glass laminate in whichmerely a slight curvature of the entire laminated panel unit will occurwhich, however, will have a negative effect neither on the opticalappearance nor on the adhesive behavior of the image layer.

[0007] For an optically attractive appearance of the laminated panelunit, it is suitable if at least one panel is transparent ortranslucent, respectively.

[0008] For a laminated panel unit having a long useful life, it isadvantageous if glass panes are provided as the panels.

[0009] An inhomogeneous laminate is reliably ensured if the twointermediate adhesive layers and/or panels are made of differentmaterials, so that during a temperature change the enclosed image layeris continuously subjected to a tension, whereby waviness and blisterformation, respectively, can be prevented.

[0010] In particular, the undesired waviness and blister formation,respectively, may reliably be avoided if the two intermediate adhesivelayers and/or panels are made of materials having different thermalexpansion coefficients. In this manner it will be ensured that the imagelayer will reliably remain tensioned by the intermediate adhesive layerand/or by the panel which has the higher thermal expansion coefficient,even when the laminated panel unit is heated, wherein a slight concavecurvature of the entire laminated panel unit will occur with regard tothe intermediate adhesive layer and/or to the panel having the higherthermal expansion coefficient.

[0011] Tests have shown that for avoiding waviness it is also suitableif the two intermediate adhesive layers have different gluing abilities,since thus the image unit enclosed by the two intermediate adhesivelayers will be differently tensioned on either side.

[0012] To form an inhomogeneous panel/image layer/panel laminate,whereby a curvature of the entire laminated panel unit will occurinstead of the image layer enclosed between the panels becoming wavy, itis also advantageous if the two intermediate adhesive layers and/orpanels have different material thicknesses. For instance, aninhomogeneous laminate will also be created if the intermediate adhesivelayers on both sides are made of the same material, have the samethermal expansion coefficient, yet the panels differ in materialthickness.

[0013] It is preferred that at least one intermediate adhesive layer isa sheet, preferably an ethylene vinylacetate copolymer (EVA) sheet,polyvinyl acetate (PVA) sheet, polyvinyl butyral (PVB) sheet or thelike. EVA sheets have proved successful in practice since, in contrastto the known polyurethane sheets, they do not require autoclaves forgluing the glass panel to the image layer. As ethylene vinyl acetatecopolymer sheets (EVA films), particularly sheets of Sekusui,Bridgestone and Takeda are preferred, the best results in terms oflaminate strength having been obtained with the S-LEX-EN film ofSekusui.

[0014] If one intermediate adhesive layer is made of a casting resin, areliable laminate of the image layer with the neighboring glass panewill be given, wherein, of course, the most varying types of castingresins may be used. In tests it has also been proved suitable that oneintermediate adhesive layer consists of silicone adhesive.

[0015] To prevent moisture from penetrating to the image layer that isenclosed between the panels, in which case the strength of the laminatedpanel unit would no longer be given and an undesired waviness of theimage layer would occur, it is advantageous if on the periphery of thepanels, at the narrow sides thereof, an external insulating layer,preferably of silicone, is provided.

[0016] If a photograph, a slide, an ink-jet, laser or silkscreen printor the like is provided as the image layer, different laminated panelunits in the widest variations can be made, and because of the simpleduplication of photographs, ink-jet, laser prints and the like, theproduction of the laminated panel unit will be particularlycost-efficient. Particularly with a view to a long-lastinglight-fastness of the laminated panel unit, when using photographs asimage layer, it is advantageous if a photograph developed according tothe silver-bleaching method (P3X-method) is provided. Here, preferablyso-called “Ilfochromfotos” of the company Ilford which have beenproduced according to the silver-bleaching method, are used, since fromall the known photographic films, they are the most light-fast ones.Such photographs also have the advantage that they have polyester ascarrier material, and consequently, together with the two adjacent(glass) panes, they will form an extremely resistant laminate, similarto bullet-proof glass. Likewise, the image layer increases the acousticinsulation of the (glass) panes, which makes them particularly suitableto be used as partition walls.

[0017] In order to achieve different optic effects with the laminatedpanel unit, it is suitable if the image layer is transparent,translucent or opaque. Here, the image layer may comprise the mostvarying carrier materials, with the carrier material in case of atransparent or translucent image layer, respectively, mostly consistingof triacetate or polyester, whereas in case of opaque image layers,polyester sheets or polyethylene paper is preferably used as the carriermaterial. The inventive laminated panel unit may thus very well be usedas a light regulating means which regulates, or reduces, respectively,incident light.

[0018] If the laminated panel unit has an area of larger than 2 m²,preferably larger than 4.5 m², it may advantageously be used forexternal applications, such as facades, windows and the like, resultingin an attractive appearance for the viewer from the outside, with theincident light simultaneously rendering the motif of the image layer inthe interior space, similar to a slide projection.

[0019] The method for producing a laminated panel unit according to anyone of claims 1 to 14 is characterized in that the image layer isconnected with area contact on either side thereof with the panels byusing intermediate adhesive layers, the intermediate adhesive layersand/or the panels having a different thermal expansion behavior. By thisproduction method in which intermediate adhesive layers and/or panelswith different thermal expansion behavior are used on either side of theimage layer, laminated panel units can be produced in which the imagelayer cannot become wavy or form blisters, respectively, even in case oftemperature changes, so that they may particularly also be used inexternal applications.

[0020] If the panels are glued together without the use of an autoclave,a production of laminated panel units is achieved which is much moreenergy-saving than known production methods in which the laminated panelunit is glued together by means of a polyurethane sheet in an autoclave.

[0021] For a reliable laminate of the image layer with the panels it isadvantageous if the laminated panel unit is glued together under anegative pressure. To increase the adhesion propensity of the imagelayer, it is advantageous if the image layer is cleaned, preferablydegreased, on either side prior to gluing.

[0022] For a simple and cost-effective production as well as for an easyapplication of a negative pressure for the gluing it is suitable if thegluing of the image layer with at least one panel is effected in aplastics envelope. In doing so, it is particularly suitable if theplastics envelope, prior to the gluing of the image layer to at leastone panel, preferably is evacuated to substantially 0.8 bar, wherebyadvantageously also the humidity in the plastics envelope is reduced. Ahigh proportion of moisture in the laminated panel unit is particularlydetrimental when using “Ilfochromfotos”, since by this thelight-fastness of the photographs is negatively affected.

[0023] If a casting resin is used as the intermediate adhesive layer, itis advantageous if at first the image layer is merely connected to afirst panel, preferably in a plastics envelope, and only in a secondmethod step a second panel is connected thereto after the image layerhas been connected to the first panel. Thus, after the first methodstep, a glue can be applied in frame-like manner to the rim of thepanel/image layer-laminate at the image-layer side thereof, whereby thesecond panel will be kept in spaced relationship from the former underformation of a cavity when being laid onto the image layer, and thecavity can be filled thereafter with casting resin.

[0024] When using sheets on both sides as intermediate adhesive layers,it is suitable with a view to an efficient, time-saving production ofthe laminated panel unit if the image layer is connected simultaneouslyto both panels.

[0025] In the following, the invention will be described in more detailand with reference to preferred exemplary embodiments illustrated in thedrawings, to which, however, it shall not be restricted. In detail, inthe drawings

[0026]FIG. 1 shows a view of a laminated glass unit in an exploded, notyet assembled position;

[0027]FIG. 2 shows a view of the laminated glass unit in an assembledposition;

[0028]FIG. 3A shows a partial region of the section according to lineIII-III of FIG. 2;

[0029]FIG. 3B likewise shows a partial region according to sectionIII-III of FIG. 2, yet with a different intermediate adhesive layer; and

[0030]FIG. 4 shows a section of a laminated glass unit comprising twoimage layers.

[0031] In FIG. 1, a laminated glass unit 1 is shown in a not yetassembled position, wherein the two glass panes 2 are visible betweenwhich an image layer 3 is glued by means of intermediate adhesive layers4, 4′ provided on either side of the image layer 3.

[0032] Prior to gluing of the image layer 3 which, preferably, is anIlfochrom-photograph, the former at first is degreased on either side soas to increase the gluing ability.

[0033] Then the image layer 3 is applied to the glass pane 2 with anintermediate adhesive layer 4 being interposed. Subsequently, the secondglass pane 2 is applied to the glass pane/image layer-laminate 1′ with asecond intermediate adhesive layer 4′ being interposed. The entire, notyet glued together laminated glass unit then is enveloped with aplastics envelope or sheet, respectively (not shown), and closed in anair-tight manner. Subsequently, a vacuum pump is connected to theplastics envelope, and in this manner a negative pressure ofapproximately 0.83 bar is produced. For gluing the image layer 3 to theintermediate adhesive layers 4, 4′, and for gluing the latter to theglass panes 2, the entire glass pane/image layer laminate is “baked” inan oven.

[0034] After termination of the gluing procedure and cooling of thelaminated glass unit, the plastics envelope is removed.

[0035] As an alternative to the simultaneous gluing of a glasspane/image layer/glass pane unit, at first the image layer 3 may also bemerely combined with a glass pane 2 into a laminate 1′, as sketched inFIG. 1 by the broken partition line 5. After the image layer 3 has beenglued to a single glass pane 2, the second glass pane 2 can be put ontothe image layer side in spaced relationship by means of a frame-likeapplied glue, and the enclosed cavity can be filled with a castingresin. Only in a second method step, the second glass pane 2 is thenglued to the already glued-together glass pane/image layer laminate 1′with the help of the second casting resin intermediate adhesive layer4′.

[0036] Upon gluing, a laminated glass unit 1 forms, as shown in FIG. 2,with a silicone adhesive 7 being applied on the periphery of the glasspanes 2 after the narrow side 6 has been glued, so as to reliablyprevent moisture from the outside from penetrating to the image layer 3enclosed between the glass panes 2; too high a proportion of moisture inthe laminated glass unit would reduce the strength of the laminate, onthe one hand, and, moreover, deteriorate the light-fastness of the imagelayer 3, if an Ilfochrom photo is used.

[0037] What is essential here is that the two intermediate adhesivelayers 4, 4′ schematically illustrated in FIGS. 3a and 3 b consist ofdifferent materials, since in this manner an inhomogeneous laminate isprovided; whereby, when heating the laminated glass unit 1, anunintended wave formation of the image layer 3 between the two glasspanes 2 is prevented. For an inhomogeneous glass pane/image layer/glasspane laminate, particularly the different thermal expansion behavior aswell as the different gluing abilities of the two intermediate adhesivelayers 4, 4′ with the image layer is responsible.

[0038] For a reliable gluing which, at the same time, does notnegatively affect the light-fastness of the laminated glass unit, inparticular sheets of ethylene vinylacetate compolymer (EVA), polyvinylacetate (PVA) as well as polyvinyl butyral (PVB), having a materialthickness of approximately 0.25-0.4 mm, are used, since the latter arealso suitable for gluing without the use of an autoclave. This in turnresults in the advantage of a substantially more energy-efficientproduction of the laminated glass unit in comparison to the gluing ofthe layers in an autoclave.

[0039] In tests, particularly a sheet of modified EVA has provensuitable which is commercially available under the name S-LEX-EN filmfrom Sekusui. Instead of the plastics sheets, however, also anintermediate adhesive layer of casting resin or silicone adhesive can beprovided which has a material thickness of approximately 1 mm.

[0040] The afore-mentioned intermediate adhesive layers 4, 4′ may bearbitrarily combined with different intermediate adhesive layers 4, 4′to obtain a laminated glass unit 1.

[0041] Particularly for an inhomogeneous laminate, it is also suitableto provide the sheets 8 on either side of the image layer 3 in differentnumbers of layers as said intermediate adhesive layers. For instance, asshown in FIG. 3b, merely a single sheet 8 may be applied as intermediateadhesive layer 4 on one side, whereas two sheets 8 are arranged one ontop of the other to form the intermediate adhesive layer 4′ forconnection with a second glass pane 2.

[0042] Besides photographs, also ink-jet, or laser prints may be used asthe image layer 3, it being possible to use different carrier materialsof the image layers 3 in each case. To produce a transparent ortranslucent laminated glass unit 1, triacetate or polyester is preferredas the carrier material. On the other hand, for producing opaquelaminated glass units, paper, polyethylene paper or also polyester filmsmarketed under the trademark Melinex may, e.g., be used as the carriermaterial for the image layer 3.

[0043] When using photographs as image layer 3, preferably copies ofpositives are used because of their high light-fastness on one of thepreviously mentioned carrier materials, whereupon the former aredeveloped by means of the silver-bleaching method. In doing so, the filmIlfochrom from Ilford is particularly preferred. On the other hand,however, also copies of negatives may be used on one of the previouslymentioned carrier materials, yet their light-fastness is poorer.

[0044] To prevent the image layer 3 glued between the glass panes 3 frombecoming wavy, it is, however, merely essential that the twointermediate adhesive layers 4, 4′ provided for gluing are made ofdifferent materials, in particular that they have different thermalexpansion coefficients and different gluing abilities, whereby, insteadof the image layer 3 becoming wavy, the entire laminated glass unit 1becomes slightly curved upon heating, wherein, however, this curvatureis so unsubstantial that it does not negatively affect the opticalcharacteristic of the laminated glass unit.

[0045] In FIG. 4, a section of a laminated glass unit comprising twoimage layers 3 can be seen. To obtain an inhomogeneous laminate,intermediate adhesive layers 4, 4′ each of the same material and withthe same material thickness are, indeed, provided in this exemplaryembodiment, yet the glass panes 2, being e.g. 2 mm, 4 mm and 6 mm, havedifferent material thicknesses, resulting in a different thermalexpansion behavior on each of the two sides of the image layers 3 and,thus, the image layers 3 will reliably remain tensioned even undergreatly changing ambient temperatures, as often occurs in case of anexternal application, e.g. when used as a facade or the like, withoutundesired waviness or blisters forming.

[0046] It goes without saying that the laminated glass unit may alsocomprise three or more image layers; what is essential is merely thatthe image layers will remain tensioned even under changing ambienttemperatures.

1. A laminated panel unit (1) comprising at least one image layer (3)between at least two panels (2), wherein for an area-contact gluing ofthe image layer (3) with neighboring panels (2), one intermediateadhesive layer (4, 4′) is provided on each side thereof, characterizedin that transparent or translucent glass panes are provided as thepanels (2), and that the two intermediate adhesive layers (4, 4′)following each im-age layer (3) have a different thermal expansionbehavior so that the image layer (3), due to the inhomogeneous laminate,is tensioned between the glass panes in case of temperature changes. 2.A laminated panel unit according to claim 1, characterized in that thetwo intermediate adhesive layers (4, 4′) are made of differentmaterials.
 3. A laminated panel unit according to claim 1, characterizedin that the two intermediate adhesive layers (4, 4′) are made ofmaterials having different thermal expansion coefficients.
 4. Alaminated panel unit according to claim 1, characterized in that the twointermediate adhesive layers (4, 4′) have different gluing abilities. 5.A laminated panel unit according to claim 1, characterized in that thetwo intermediate adhesive layers (4, 4′) have different materialthicknesses.
 6. A laminated panel unit according to claim 1,characterized in that at least one intermediate adhesive layer (4, 4′)is a sheet, preferably an ethylene vinylacetate copolymer (EVA) sheet,polyvinyl acetate (PVA) sheet, polyvinyl butyral (PVB) sheet or thelike.
 7. A laminated panel unit according to claim 1, characterized inthat one intermediate adhesive layer (4, 4′) is made of a casting resin.8. A laminated panel unit according to claim 1, characterized in thatone intermediate adhesive layer (4, 4′) is made of silicone adhesive. 9.A laminated panel unit according to claim 1, characterized in that onthe periphery of the panels (2), at the narrow sides (6) thereof, anexternal insulating layer (7), preferably of silicone, is provided. 10.A laminated panel unit according to claim 1, characterized in that aphotograph, a slide, an ink-jet, laser or silkscreen print or the likeis provided as the image layer (3).
 11. A laminated panel unit accordingto claim 10, characterized in that a photograph developed according tothe silver-bleaching method is provided.
 12. A laminated panel unitaccording to claim 1, characterized in that the image layer (3) istransparent, translucent or opaque.
 13. A laminated panel unit accordingto claim 1, characterized in that the laminated panel unit has an areaof

larger than 4.5 m².
 14. A method for producing a laminated panel unit(1) according to claim 1, characterized in that the image layer (3) isconnected with area con-tact on either side thereof with the glass panes(2) by using intermediate adhesive layers (4, 4′), the inter-mediateadhesive layers (4, 4′) having a different thermal expansion behavior.15. A method according to claim 14, characterized in that the glasspanes (2) are glued without the use of an autoclave.
 16. A methodaccording to claim 14, characterized in that the laminated panel unit(1) is glued together at a negative pressure.
 17. A method according toclaim 14, characterized in that the image layer (3) is cleaned,preferably degreased, on either side before gluing.
 18. A methodaccording to claim 14, characterized in that gluing of the image layer(3) with at least one glass pane (2) is effected in a plastics envelope.19. A method according to claim 14, characterized in that the plasticsenvelope, before the image layer (3) is glued to at least one glass pane(2), is evacuated, preferably to substantially 0.8 bar.
 20. A methodaccording to claim 14, characterized in that after connecting the imagelayer (3) to the first glass pane (2), a second glass pane (2) isconnected thereto.
 21. A method according to claim 14, characterized inthat the image layer (3) is simultaneously connected to the two glasspanes (2).